The present invention is concerned with the art of securing abrasion resistant members such as ceramic tiles to metallic surfaces to protect the surfaces against abrasion.
Apparatus such as centrifuges, pneumatic conveyors, conveyor pipes, vibrating feeders, feed chutes and a multitude of other such apparatus are commonly used to convey abrasive and/or chemically destructive material such as coal fines, ceramics, cement, lime, grain and glass. When these materials are conveyed in direct contact with the metallic surface of the apparatus, excessive and expensive wear occurs due to the abrasive or chemical action of the materials with the metallic surface of the apparatus.
For a number of years, the metallic surfaces of apparatus as the foregoing have been protected by lining the effected areas thereof with ceramic tiles. These tiles come in various lengths, widths and thicknesses depending upon the particular application. As an example, a typical tile would be 1/2 inch thick and, for flatware, 3.times.6 inches in width and length and for curved material of approximately the same thckness and length and width but formed on a radius for the desired curved surface. These tiles are basically alumina which is extremely hard and thus wear resistant and also resistant to chemical attack.
One manner of securing the tiles in place is to use an adhesive material on the surface of the tile to be placed into engagement with the metallic surface. One of the drawbacks of this arrangement is that the adhesive material does not provided the required bonding force in many cases and also does not hold up well in environments where the material being conveyed is at an elevated temperature.
Another application or method for securing the tiles in place is to provide an aperture within the tiles which, in some cases, may be tapered. The tiles are positioned upon the metallic surface to be lined and a conventional stick welding apparatus is used to form a plug weld within the aperture to secure the tile in place. Another variation of this method is to place a split metallic ring within the aperture which is forced into place within the aperture and to weld the ring by the conventional stick welding process to the metallic surface.
There exists a third method and/or structure for securing the ceramic tile in place to the surface to be lined. In this instance, the tiles also include a tapered aperture within the tile. An end weldable stud is used where the stud is likewise tapered at an angle corresponding to that of the taper of the aperture of the tile. The outer dimension of the stud is slightly greater than the dimension of the taper within the tile at the point of minimum dimension of the taper. The stud is placed within the aperture of the tile toward the point of minimum dimension of the taper thereof and into contact with the metallic surface to be lined and welded in place by the stud end welding technique. As the stud melts at its end being welded, the stud is pulled downwardly into the taper of the aperture of the tile to secure the tile in place upon the metallic surface to be lined.
The method or procedure for securing tiles to metallic surfaces wherein a conventional stick welding apparatus is used has the drawback that the stick welding is extremely slow and is thus expensive. Likewise, the tapered metallic stud utilized in the alternate procedure includes a rather substantial amount of material and also is of a configuration that must be made upon a screw machine rather than upon a cold header. For this reason, while the tapered plug can be welded more efficiently and inexpensively by the stud end welding process, this advantage is taken away by the excessive cost of the tapered stud itself due to the inclusion therein of the excessive material and the expensive method of manufacturing upon a screw machine. In both instances wherein either the conventional stick welding is used to form a plug weld or the tapered stud is used, there is the further problem encountered that the tile is only secured against the surface by the relatively loose fit of the plug weld or tapered stud weld to the metallic surface. Any expansion of the material or vibration can cause the tiles to become loose with the ultimate result of fracture and loss of the tile.
The afore-described methods and means for securing ceramic tiles to metallic surfaces to be lined for protection against abrasion all include the common drawback of excessive expense, and or time consuming in installation, and/or lack of ability to withstand elevated temperatures and finally, the inability to provide a strong and resilient interconnection of the tile with the metallic surface. The industry needs an inexpensive tile fastening system both in material costs and in installation time which will provide a strong and resilient bond of the tile to the metallic surface to be lined with the abrasion resistant material.